In clinical practice brachytherapy applications are gaining importance. In the course of a brachytherapy treatment a radioactive source, usually a gamma emitter, is introduced into a target volume of a patient. The radioactive source may be introduced manually or using an afterloader device. Generally, the afterloader device is used for providing the radioactive source or sources inside the patient for a given (short) period of time inside pre-positioned catheters. In such a case, the gamma source may be a high dose rate source or a low dose rate source. Alternatively, the sources (seeds) may be provided inside the target volume of the patient for a prolonged (several hours) or permanent dwelling. Such sources may be low dose rate sources. Usually, a suitable radioactive source is accommodated in a catheter or a needle adapted for enabling introduction of the radioactive source into a vessel, a cavity, or a tissue volume.
It is a disadvantage of the contemporary brachytherapy that the actual source position in a patient is verified indirectly. For example, generally, suitable X-ray imaging may be used for determining the position of a source body or source bodies inside the patient (or a catheter introduced inside the patient). However, such an approach may be not sufficiently accurate or reliable in certain circumstances, for instance when a train of sources, such as active rods, is being provided, wherein the active rods are being interleaved with non-active spacers which fully imitate the geometry of the radioactive sources.
US2003/0153850 discloses a TRUS probe having glued stainless steel balls as fiducial markers, under ultrasound. Gadolinium impregnated materials are mentioned to be used as fiducial markers for MRI.
Us2010/0041938 discloses the use of contrast filled ellipses and contrast filled spheres as MRI/CT markers, at a frontal part of a needle delivery system.